FIG. 1 is a sectional illustration of a conventional nuclear reactor fuel assembly 10 typically used in commercial light water nuclear reactors for electricity generation throughout the world. Several fuel assemblies 10 are shipped to and placed in a reactor in close proximity to sustain a nuclear chain reaction. A fluid moderator and/or coolant conventionally passes through fuel assembly 10 in an axial direction, enhancing the chain reaction and/or transporting heat away from the assembly 10.
As shown in FIG. 1, fuel assembly 10 includes multiple fuel rods 14 containing fissile material and extending in the axial direction within the assembly 10. Fuel rods 14 are bounded by a channel 12 that forms an exterior of the assembly 10, maintaining fluid flow within assembly 10 throughout the axial length of assembly 10. Conventional fuel assembly 10 also includes one or more conventional fuel spacers 18 at various axial positions. Fuel spacer 18 permits fuel rods 14 to pass through grid-like openings in spacer 18, thereby aligning and spacing fuel rods 14. One or more water rods 16 or other assembly features may also pass through spacer 18, and grid size and shape, and the overall shape of spacer 18 may vary across different designs of assembly 10.
As shown in FIG. 1, fuel spacer 18 may include one or more bathtubs 44 that extend from spacer 18 and contact internal surfaces of channel 12. For example, as shown in FIG. 1, multiple bathtubs 44 may be on each face of fuel spacer 18 extending out toward channel 12. In this way, bathtub 44 may keep fuel spacer 18 rigidly aligned within and spaced from an internal surface of channel 12. Bathtubs 44 may be welded to, fastened to, clamped on, or deposited on fuel spacer 18 at desired points in any number necessary to secure spacer 18 within channel 12. Similarly, bathtubs 44 extend a length required to entirely close any gap between spacer 18 and channel 12, such that the two are always in rigid contact.